Full Subtractor

 A full subtractor is a combinational circuit that performs subtraction involving three bits, namely A (minuend), B (subtrahend), and Bin (borrow-in) . It accepts three inputs: A (minuend), B (subtrahend) and a Bin (borrow bit) and it produces two outputs: D (difference) and Bout (borrow out). The logic symbol and truth table are shown below.




Figure-:Logic Symbol of Full subtractor

Figure-:Truth Table of Full subtractor

From the above truth table we can find the boolean expression.

D = A ⊕ B ⊕ Bin
Bout = A' Bin + A' B + B Bin

From the equation we can draw the Full-subtractor circuit as shown in the figure.


Figure-:Circuit Diagram of Full subtractor

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